Droid doesn't always "lock"Support

So really the only main gripe that I can find about my droid (have had it since just after Christmas this past year, is that when the screen goes to sleep it doesn't always lock.

I don't have the lock pattern activated, if I do activate it though the phone locks just fine like it's supposed too. Basically whenever the phone goes to sleep if I wake it back up again by hitting the button on the top, it will sometimes be locked and sometimes just open to the home screen. I would prefer it be locked with the basic, stock, slide to unlock feature.

I'm guessing there is an addon that is causing this intermittent issue but I can't say for sure, or is there a setting I'm missing somewhere? The screen timeout I use is 30 seconds.